This application pertains to subject matter included in U.S. Pat. No. 5,144,619, titled "Common Memory Switch For Routing Data Signals" granted to E. A. Munter, and which is incorporated herein by reference.
1. Field of the Invention
This invention relates to packet switching in general and particularly to a method and apparatus for switch partitioning. More specifically, this invention relates to a method and apparatus for switch partitioning which minimizes the functionality of an asynchronous transfer mode (ATM) cross point matrix to that strictly necessary at the centre of the switch.
2. Prior Art of the Invention
In a paper titled "Architectual And Functional Aspects Of A Multi-Media Packet Switched Network" by Takami, K., et al, Proc. ISS, 1987, the authors discuss a network architecture based upon the core and edge concept, in which the core of the switch offers common functions to all media, while the edge offers media dependent functions. The paper discusses a layered structure of functions for the entire network. And while "core interface" (CI) between the edge and the core is described as using only packet transmission functions, the structure of the CI itself is not discussed in this paper.
In another paper titled "Wideband Packet Technology For Switching Systems" by Luderer, G. W. R., et al, Proc. ISS, 1987, the authors state:
The network hardware can support virtual circuits as well as datagram type services. For the virtual circuits, a logical Channel Number (LCN) is used to represent a destination. To create a new virtual circuit between two AIs [AI: Access Interface], it is necessary to assign LCNs for all links that are used for routing packets for that virtual circuit. The LCN assignments are done by the call processors at the time of call setup. A packet that enters a switch with an LCN number LCN.sub.--in leaves the switch with a translated LCN number LCN.sub.--out. The LCN translation is done in the trunk controllers by a simple table look-up procedure. The call processor is responsible for updating the translation tables in the trunk controllers. One virtual circuit may pass through several switches and transmission facilities; a packet originating at an AI may therefore use different LCNs along different links that form the path from the source to the destination. A 16-bit LCN field supports 65536 virtual circuits per switch; a network of several switches can therefore support a very large number of virtual circuits. It is also possible to implement many other routing techniques; the LCN-based scheme is intended to serve as an example and was actually implemented in some of the early experiments. In order to switch interactive voice signals through a packet network, we used a Time Step (TS) field as a part of the header to facilitate reconstruction of time-critical information. Other fields in the packet header can be used to support applicant-dependent features including a priority field for special services. The next section will address some of these issues in the context of a single packet switch.
The present invention endeavours to provide operator flexibility by isolating the switch matrix from incoming and outgoing LCNs.